The invention relates to a method for detecting the load of items to be washed in a dishwasher machine in which the items to be washed are placed in receptacles in the washing chamber of the device, wherein the loading of the receptacles for the items to be washed is detected by an image detection system. The invention further relates to a dishwasher for carrying out the method.
Program-controlled dishwashing machines, in particular used in the household, can be operated in an energy-saving manner by setting the power and water consumption in relation to the quantity of crockery or items to be washed which is loaded in the receptacles for washing.
For example, it is known from EP 0 943 287 A1 to arrange sensors for detecting electromagnetic waves and/or sound waves a large distance apart from one another in the washing container of the device, in particular on a spatial diagonal, wherein each sensor is assigned a transmitter which transmits light signals or acoustic signals. When the transmitter emits signals, these are partially reflected by the loaded items to be washed and/or optionally reach a receiver (sensor) in a time-delayed manner. The temporal evaluation of the signals received by the sensors then gives an indication of the arrangement of the items to be washed or the quantity of crockery. The quantity of crockery or the load of items to be washed determined in each case is registered and the sequence of the washing program for treating these items to be washed is influenced. This can take place, for example, by supplying washing liquid into the washing container according to the load and by heating the washing liquid adapted to the load.
A disadvantage of this arrangement can be seen in that crockery parts located in the transmission beam of the signal emitter reflect and deflect the electromagnetic waves or acoustic waves emitted by the transmitters with the result that items to be washed optionally positioned therebehind in the crockery basket are not precisely detected despite the diagonal alignment of the transmitter and receiver. The load recognition is therefore inaccurate and additionally provides only a two-dimensional image of the loading of the receptacle for the items to be washed.
DE 100 48 081 A1 further discloses to provide one or more separate image detection or image detection systems as well as one or more lighting devices to detect the type and quantity of the loading of items to be washed in the washing container and/or on the side of the appliance door facing the washing container. In this case, the image detection systems can be embodied in the manner of commercially available black/white and/or colour mini cameras (mini cameras).
A disadvantage of this arrangement is that camera systems of the specified type are expensive and are not designed per se for use in water-carrying appliances. In addition, sufficiently strong lighting must be provided in the washing chamber to create sufficient brightness for the image detection system to photograph the washing chamber. In addition, the proposed system can only produce a two-dimensional image of the items to be washed positioned in the washing chamber.
The use of an optical scanning device in the fashion of a laser scanner is also known for detecting the load of a dishwasher machine, said scanner being disposed in front of the washing chamber opening to detect the items to be washed. The laser scanner derives information on the type of crockery items by image detection of the items to be washed, wherein corresponding signal patterns are generated by the scanner and fed to the program controller. The loading quantity is determined in this case by counting the crockery items loaded in the washing container. Such a dishwasher machine is described in DE 100 48 086.
A similar principle is used in EP 1 192 893 A2, where a light curtain is disposed in the washing chamber opening and the crockery load of the washing container can be concluded from the profile of the light interruptions thus produced.
Finally, the use of a camera is known from DE 101 62 505 A1, this camera being used to identify items to be washed with particularly stubborn contamination so that these crockery items can then be subjected to more intensive cleaning.
So-called photonic mixer devices (PMD) which can determine three-dimensional distance images are known as alternative sensors. Such photonic mixer devices or photomixing detectors are described in DE 197 04 496 A1. In order to determine the phase and/or amplitude information of an electromagnetic wave, a pixel of a photonic mixing element has at least two light-sensitive modulation photogates and allocated accumulation gates. Gate voltages are applied to the modulation gates whereas a DC voltage is applied to the accumulation gates. The charge carriers generated by an incident electromagnetic wave in the space charge zone of the modulation photogates are exposed to the potential gradient of a drift field depending on the polarity of the gate voltages and drift to the corresponding accumulation gate. Photomixing detectors of the type described in this document are used in automobile-related applications to detect impending collisions from the three-dimensional images determined of the surroundings and to initiate countermeasures.